The present invention relates to a clamp device which is used in connecting a newly laid branch pipe to a pipe which is buried under the ground, for instance, a gas main or water main pipe.
In connecting a branch pipe to a gas main pipe (or water main pipe), a branched coupling is fitted to a section of the main pipe. In the case of a cast gas main pipe, the gas main pipe is provided with a threaded hole and the branched coupling is screwed directly into this hole for connection.
If, however, the gas main pipe is made of steel, this pipe itself has a thinner thickness, and hence to join the branched coupling directly to it, as in the case of a cast pipe, is problematic with respect to strength. For this reason, a clamping device, having a construction as shown in FIG. 1, is now being employed. This clamping device 1 consists of two split structures which are the upper frame 2 and the lower frame 3 that are secured by bolts 4 and nuts 5. To connect this type of clamping, a vertical hole 10, as shown in FIG. 2, is excavated and the gas main pipe 6 is exposed. A worker enters the vertical hole 10, places the upper frame 2 on the gas main pipe 6, positions the lower frame 3 under the pipe, securing both these components with bolts 4 and nuts 5, and then connects the branched coupling 9 to a connection port 7 of the upper frame 2. The worker then connects the branch pipe 8 to the branched coupling 9.
In the connection work for this conventional clamping device, as clearly seen from the aforesaid working example, one worker at least must enter the vertical hole to perform the work. This fact, however, had disadvantages which are listed below:
(a) Trouble and time are consumed for excavating the vertical hole. PA1 (b) Trouble and time are also necessary for burying the vertical hole, and in the case where a paved street is over the point of connection, a large repair trace remains on the surface. PA1 (c) If the space is not available to excavate the vertical hole large enough to accommodate a worker, the branched pipe must be extended all the way to the place where such space is available.